Turbine systems are widely utilized in fields such as power generation. For example, a conventional gas turbine system includes a compressor section, a combustor section, and at least one turbine section. The compressor section is configured to compress air as the air flows through the compressor section. The air is then flowed from the compressor section to the combustor section, where it is mixed with fuel and combusted, generating a hot gas flow. The hot gas flow is provided to the turbine section, which utilizes the hot gas flow by extracting energy from it to power the compressor, an electrical generator, and other various loads.
The combustor sections of turbine systems generally include tubes or ducts for flowing the combusted hot gas therethrough to the turbine section or sections. Recently, combustor sections have been introduced which include tubes or ducts that shift the flow of the hot gas. For example, ducts for combustor sections have been introduced that, while flowing the hot gas longitudinally therethrough, additionally shift the flow radially or tangentially such that the flow has various angular components. These designs have various advantages, including eliminating first stage nozzles from the turbine sections. The first stage nozzles were previously provided to shift the hot gas flow, and may not be required due to the design of these ducts. The elimination of first stage nozzles may eliminate associated pressure drops and increase the efficiency and power output of the turbine system.
However, the aerodynamic efficiency of currently known transition ducts is of increased concern. For example, recent studies have shown that hot gas flows through such transition ducts have relatively high aerodynamic losses, in particular relatively high pressure losses. Further, such studies have indicated the production of relatively high wakes in the downstream portions of the transition ducts, resulting in non-uniform flow and high unsteady mixing losses downstream thereof. Due to such non-uniform flow and unsteady mixing, first stage buckets in the turbine sections may be subjected to high cycle fatigue loads and thermal loads, which may significantly reduce the durability of the buckets.
Accordingly, an improved transition duct for use in a turbine system would be desired in the art. For example, a transition duct that provides increased efficiency values would be advantageous. Further, a transition duct which minimizes mixing losses, thus reducing overall pressure losses and increasing system performance and efficiency, would be advantageous. Still further, a transition duct which reduces high cycle fatigue loads and thermal loads on turbine section first stage buckets would be advantageous.